University of California • Berkeley

Gift of
FRANCIS P. FARQUHAR

DEPARTMENT OF THE INTERIOR

FRANKLIN K. LANE. SECRETARY

NATIONAL PARK SERVICE

STEPHEN T. MATHER. DIRECTOR

THE

VOLCANIC HISTORY

OF LASSEN PEAK

Lassen Volcanic National Park, California

View of Lassen Peak looking southeast from near Manzanita Lake. A small jet of steam from the ciater
is being blown to the south

By

]. S. DILLER

Geologist, United States Geological Survey

With an Introductory Note on the National Park

WASHINGTON

GOVERNMENT PRINTING OFFICE
1918

INTRODUCTORY NOTE.

While volcanoes occur in many parts of the United States, the vol-
canic field which has affected our scenery in the most distinguished
manner lies in our Northwest. It includes no less than three national
parks in the Cascade Mountains, Mount Rainier, Crater Lake, and
Lassen Volcanic, and, farther east in Wyoming, the celebrated Yel-
lowstone. Lassen Peak lies in northern California, at the southern
end of the Cascade Mountains. Its period of relatively small erup-
tions since the spring of 1914, following upon a quiescent period of
about 200 years, centered the national gaze upon it and Congress
created it a national park on August 9, 1916. It is the only volcano
in the United States now regarded as active, although Mount St.
Helens and Mount Baker have been active within recorded history.

Since the close of its period of most vigorous activity in 1915, Las-
sen Peak has remained comparatively quiet. Many hot springs and
other minor phenomena attest its condition of internal heat, and
from time to time, at decreasing intervals, the volcano emits quantities
of steam and smoke. There may be later explosions, but Lassen's
history as a dying volcano offers a reason for not expecting great out-
breaks. It may be classed to-day between semiactive and active.

Lassen Volcanic National Park offers to the visitor an exhibit of
volcanic forces in semiaction which is interesting and instructive.
The Peak rises 10,460 feet in altitude. Cinder Cone rises 6,907 feet.
There are smaller volcanic peaks and lava fields, fumaroles, hot
springs, and mud volcanoes or solfataras, as well as boiling lakes and
other interesting phenomena of a volcanic region. There are also
many cold lakes and trout streams in majestic forested tablelands and
canyons. The national park contains 124 square miles.
2

THE VOLCANIC HISTORY OF LASSEN PEAK.1

By J. S. DILLER.

Lassen Peak is in northeast California and forms the southern end
of the Cascade Range. It stands between the northern end of the
Sierra Nevada and the Klamath Mountains, a mighty volcano that
rises to an elevation of more than a mile above the early Tertiary and
Cretaceous sedimentary rocks on which it rests. It is on the edge of
one of the greatest lava fields in the world, extending from northern
California, Oregon, and Washington eastward across Idaho into the
Yellowstone National Park of Wyoming, and covering an area of
about 250,000 square miles. Over the eastern portion of this field
most of the lava is basalt, which was very liquid at the time of its
eruption and, spreading far and wide like water, it formed a flattish
country, the great plains of Snake River and the Columbia, but along
the western border the lava is chiefly andesite, a viscous lava that
piled up about the vents from which it issued and built up a range,
the Cascade Range, surmounted by great peaks, from Lassen Peak,
which rises 10,460 feet, to Shasta and Rainier, that attain an eleva-
tion of more than 14,000 feet.

In the volcanic belt of the Alaskan coast there are a number of
vigorously active volcanoes. So also in Central America and Mexico,
but in the Cascade Range the volcanoes appear to be near extinction.

Since the white man settled on our Pacific coast there has been but
little volcanic activity. In 1843, about the time Fremont, the path-
finder, made his memorable trip across the continent, Mount Baker
and Mount St. Helens in the State of Washington were both in erup-
tion, spreading a blanket of volcanic dust over the country as far
south as the Columbia, where at The Dalles a missionary gave a
sample to Fremont.

Prof. Davidson, of the United States Coast Survey, in 1854 saw an
eruption of Mount Baker. The summit was obscured by vast rolling
masses of dense smoke, which in a few moments reached an estimated
height of 2,000 feet above the summit and soon enveloped it entirely.
In 1858 Mr. J. S. Hittell sawT the clouds over Mount Baker brilliantly
illuminated by an eruption then taking place.2

1 Published by permission of Director of TJ. S. Geological Survey. Reprinted from
Science, May 26, 1916.

2 " The United States," J. D. Whitney, p. 115.

52316°— 18 o

4 VOLCANIC HISTORY OF LASSEN PEAK.

Mount Rainier and Mount Shasta emit heated vapors from the
fumaroles on their summits, giving evidence that their interiors are
still hot.

The present activity of Lassen Peak, though feeble as compared
with its earlier eruptions, is proof that it must still be classed as an
active volcano.

The volcanic activity which resulted in the upbuilding of Lassen
Peak began near the close of the Eocene. The lava flows appear to
have been largest and most numerous in the Miocene and Pliocene,
successive flows decreasing in size during the Quaternary to near
extinction in recent times.

\LASSEN ^Lane "s

I VOLCAM/C
NAT/ONALPARK -_...„

AHESBA0 /N-^^0^52^

FIG. 1. — Lines of approach to the Lassen Volcanic National Park railroads, wagon roads,
and trails to Lassen Peak and Cinder Cone, which are 10 miles apart and within the
boundary of the park.

There were long periods of interrupted activity separated by long
intervals of quiescence. During the active periods both explosive
and effusive eruptions were common; the one forming cinder cones
and sheets of volcanic agglomerate and tuff ; the other forming lava
fields whose ruggedness was proportional to the viscosity of the
erupting lava.

Lassen Peak is a volcano of large type surrounded by many smaller
ones of later date, the whole being built up of a notable variety of
lavas. The oldest lavas of the Lassen Peak region are of interme-
diate chemical composition belonging to andesites. The early magma
yielding the erupting andesitic lavas in the course of time differ-
entiated into two portions. On the one hand it became more sili-

VOLCANIC HISTORY OF LASSEN PEAK. 5

ceous (salic), erupting as dacite and rhyolite, and on the other hand
it became less siliceous (mafic), yielding basalt and quartz basalt.
All varieties are well represented in the Lassen Peak region and are
derived apparently from the same magma.

As the volcanic center developed the most active crater migrated.
The first crater was in the head of Mill Creek. It was not only the
oldest, but also the largest crater, more than a mile in diameter.
Composed of andesitic lavas, it rose to a height of 9,400 feet. The
peak named " Brokeoff Mountain " on the Forest Service maps is
the most prominent remnant of this great crater in the head of Mill
Creek.

The second great crater opened on the northern edge of the first
and erupted dacite, building up Lassen Peak to its present height
with a summit crater about a quarter of a mile in diameter.

The third crater, about 4 miles a little west of north from the first,
opened only a few centuries ago at the northwest base of Lassen Peak,
and the rugged lava flows from it formed Chaos Crags.

The products of this eruption in Chaos Crags are well preserved
and their relations clearly visible. The eruption began by a succes-
sion of explosions that spread a thin layer of volcanic sand and dust
over the surrounding country and ended in the extravasation of a
most rugged mass of dacite which, though at first glance having the
aspect of granite, is rich in volcanic glass, generally of dark color,
somewhat pumiceous and full of inclusions like the dacites of Lassen
Peak.

The fourth crater of Lassen Peak is the new crater, active at the
present time. It began by a slight explosion within the old crater,
second of those enumerated, on the summit of Lassen Peak, and is
remarkable for its place of outbreak, as well as its low energy, the
small mass of material erupted and the continuity of the activity.
Like the eruption of a few centuries ago at Chaos Crags, it had two
phases, one explosive, the other effusive.

During the first phase the explosive eruptions were of gas carrying
out with it rock fragments and dust only. The size of the crater
increased with each eruption, as shown in figures 2 and 4. The second
phase, which is effusive, includes also an eruption of lava, which
formed a lid on the volcano and overflowed to the west, as represented
in figure 3.

In the beginning the new crater was confined to the loose material
filling the old crater, but later it reached the solid rock of the old
crater rim and finally after more than 150 eruptions it attained near
the end of March, 1915, a size of about TOO to 1,000 feet.

Ejecta accumulated on the rim of the new crater to a depth of 30
to 40 feet. The largest stone ejected was 15 feet in diameter and
weighed about 63 tons. Small stones were thrown as much as a mile

6 VOLCANIC HISTORY OF LASSEN PEAK.

i

from the crater, but beyond 2 miles from the crater scarcely more
than a trace of dust could be noticed except to the northeast, the
direction of the strongest winds and that taken by the great blast of
the eruption May 22, 1915.

By far the greatest eruptions that have occurred at Lassen Peak
since its present activity began are those of the night of May 19 and

FIG. 2. — Summit of Lassen Peak, Cal., above the 9,500-foot contour, as seen from above,
showing the summit spurs radiating from the rim of the old crater, within which the
small new crater (white), as it appeared October 1, 1914, contains a jet of steam.

The new crater elongated and widened (Fig. 4) by successive eruptions until about
the end of March, 1915, when it occupied by far the greater portion of the old crater,
and then the bottom began to upheave.

Modeled by the U. S. Geol. Survey. Cast at Howell's Microcosm, Washington, D. C.,
where reproductions may be obtained.

the afternoon of May 22, 1915. The first great result was the ex-
trusion of new lava and the formation of a lava lid which culminated
in the second great feature, the devastation of the Lost Creek and
Hat Creek country by horizontal blasts of hot gas.

About the end of March, 1915, the old crater having been
thoroughly cleaned out by explosive eruptions and the superincum-

VOLCANIC HISTORY OF LASSEN PEAK.

bent load largely removed from the magma, it began to rise in the
volcanic conduit and initiated the second stage, the effusive stage,
of the volcanic activity. The hot magma apparently more or less
viscous in the volcanic conduit, was forced upward by pressure of
magma or gas from beneath and was gradually upheaved, with great
escape of steam, until it reached the surface as new lava, and as a

SUMMIT or

/flffer the erupt.or, of May Zi, ;3iS.

Mod*;eo by U.S 'Geologi
Cpst at Howeii's Microc

FIG. 3. — The upheaval of the bottom within the new crater began probably about April
1, 1915, and, continuing through April and early May, culminated in the great eruption
of May 22, 1915, which resulted in the extrusion of a mass of new lava, so that it filled
both the new and old craters to the rim as a " lid," and, overflowing through the notch,
the new lava extended a short distance down the west slope. The hot blast that
devastated the Hat Creek country escaped from beneath the edge of the lava lid at the
head of Lost Creek.

Jets of steam are shown on the northeast slope. The jets of steam from the north-
west fissure and on the west slope are not clearly visible in the high light.

lava table filled not only the new, but also the old crater so as to form
a lid on the volcano. The lava overflowing from the edge of the lid
through a notch in the old rim, as shown in figure 3, passed down the
west slope of Lassen Peak about 1,000 feet.

On the night of May 19 and especially also on the afternoon of
May 22, 1915, the eruptions were violent. A mushroom-shaped cloud

8 VOLCANIC HISTOKY OF LASSEN PEAK.

was hurled to the height of about 4 miles above the summit of the
mountain and afforded a magnificent spectacle as seen from the Sac-
ramento Valley. At night 1 flashes of light from the mountain sum-
mit, flying rocketlike bodies and cloud glows over the crater reflect-
ing the light from incandescent lavas below were seen by many ob-
servers from various points of view and appear to indicate that much
of the material erupted was sufficiently hot to be luminous.

Prof. R. S. Holway, who was one of the first observers to ascend
the mountain after the eruption, saw it on May 27, five days after

FIG. 4. — Looking northwest from the rim of the old crater across the new crater,
August 17, 1914, after it had been enlarged by 25 eruptions. The sand and
bowlders ejected from the new crater cover all the slopes of the old crater in view
and the deposits are stratified as seen on the inner slope of the new crater.
Photo © by P. J. Thompson.

the eruption, and states that " hissing steam was escaping from many
cracks and crevices and the shimmering air above all telling of the
hot rocks below."

J. M. Howell's party visited the summit May 30, eight days after
the eruption, and Mr. Spaulding reports that " the heat from the up-
heaved mass was intense. The air above it shimmered with heat
waves like the desert on a boiling summer day."

That the new lava in the lid at the time of its eruption was so hot
at least in spots as to be luminous appears evident and it is probable

1 Luminous phenomena were reported on the nights of September 29, 1914, May 14, 15,
17, and 19, 1915, as well as June 20 and October 20 of the same year. Some of the
phenomena reported may be explained as due to the reflected rays of the setting sun, but
this can not be true of all.

VOLCANIC HISTORY OF LASSEN PEAK. 9

that the temperature to produce luminosity, say 600° to 1,000° C.
Avould at the same time give to the slowly rising lava such a degree
of viscosity as to enable it to adjust itself to its surroundings and
overflow the crater rim.

Although the lava lid in places appears to be a mass of tumbled
rock fragments, yet there are large portions of it essentially continu-
ous, as if forced up in viscous condition and broken later as a result
of the cooling, flowing and subsidence of the mass within the crater.
The postmaster at Manton reports that a change was noticed on
the summit of the mountain for a few days previous to May 19. A
black wedge-shaped mass of lava appeared in the middle of the new
crater, getting higher every day, and finally in plain view spilling
over through the notch on the west slope.

Many volcanic bombs were ejected by explosive eruptions during
the effusion of the new lava. They range up to 5 feet or more in
diameter and are most abundant at the foot of the steeper portion
of the northwest slope. Many of them have a peculiar compact crust
with a cracked surface like bread crust, suggesting the name " bread-
crust bombs," and they are regarded as the luminous ejecta seen in
connection with several eruptions by observers from different points
of view. Very few other portions of the erupted magma afford such
impressive evidence of fusion as the bread-crusted bombs.

Although the extrusion of the new lava and the formation of the
lava lid was the main feature of the great eruptions in May, it was
far surpassed in interest and wonder by the remarkable horizontal
eruptions of the hot blasts that devasted Lost and Hat Creeks.

On the night of May 19 it appears that the body of superheated
gases which accumulated beneath the lid, forcing it up, escaped
from under the edge with terrific force down the deep snow-covered
northeast slope of Lassen Peak toward Lost Creek and Hat Creek.
The snow was instantly converted into water, and the mighty onrush
of water and blast of hot gases swept everything before it for more
than 10 miles along Lost Creek, forming a devastated belt from a few
hundred yards to a mile in width. Meadows were buried beneath
finer debris and occasional large bowlders broken off from the edge
of the lava lid far above. Trees 3 feet in diameter were broken off
or uprooted and the country scoured as by a mighty sand-blast (Figs.
5 and 6). The fine green leaves of the pine trees left standing along
the borders of the blast were killed by the heat and turned brown.
Locally, on favorable slopes, the heat was so great that the green
leaves were charred ; not only those of the pine but also those of the
Manzanita, several acres of which, at a distance, had the general
appearance of an area swept by a forest fire. In fact, it is stated
by Mr. Fred Seaborn, of the Forest Service, who was in that region
a few days later, that two fires were actually kindled by the eruption.

10

VOLCANIC HISTORY OF LASSEN PEAK.

This reminds one of the hot blast from Mount Pelee that destroyed
St. Pierre. Luckily in the Hat Creek region there were only a few
summer residents. Warned by the noise of the approaching torrent,
they escaped to the hills.

That no one was killed was simply a matter of good fortune on the
part of the 11 enthusiasts who early visited the region to make a
photographic record. Mr. B. F. Loomis, the veteran photographer
of Viola, was among them.

There were two hot blast eruptions into the Hat Creek country;
one on the night of May 19 and the other on the afternoon of May 22.

PIG. 5. — The divide between Lost Creek and Hat Creek alter the hot blasts uprooted
the trees and scoured them with flying sand. On the border of the devastated
area the green leaves of the pines were scared and locally scorched by the hot gasses
to a distance of more than 2 miles from the crater.

The Loomis party arrived on the scene about noon, May 22, and
spent several hours photographing up to the head of Lost Creek,
making a record of what was accomplished by the first blast. They
left soon after 3 o'clock and had scarcely reached the west side of
Chaos Crags when the most violent eruption occurred, sending its
column of smoke to a height of more than 20,000 feet, as seen from
the Sacramento Valley, and a hot blast down the slope into the Hat
Creek country that would probably have killed the whole party had
the eruption occurred a few hours earlier.

At the time of the great outbreak a fissure was opened running
from the summit northwest about 1,000 feet down the slope toward
Chaos Crags. Three vents were opened on this fissure, and the

VOLCANIC HISTORY OF LASSEN PEAK.

11

greater portion of the volcanic activity during the summer of 1915
was confined to this fissure. G. W. Olsen, who ascended Lassen
Peak October 19, 1915, reported the northwest fissure quiet, but an-
other one active a few hundred feet east of it on the northern rim
of the lid.

Fumaroles have developed at a number of points on the north and
west slopes of Lassen Peak within 800 feet of the summit, but
all the violent eruptions have occurred at or very near the summit.
No fumaroles have appeared on the south and east slopes, the direc-
tion of easiest approach, where at lower levels, 5,800 to 7,400 feet,
fumaroles and solfataras are such active features at Bumpass Hell,
the Devils Kitchen, and Tartarus or Boiling Lake. These solfataras

FIG. 6.— From the lower end of Jessen's Meadow, showing the once rich pastures
converted into a waste of sand, gravel, and bowlders. In the foreground are the
logs of pines which once stood on the divide between Lost and Hat Creeks.

within 3 miles of Lassen Peak have been active with but little change
during the last 50 years. They are on the strongest side of Lassen
Peak and have not been affected by the eruptions at its summit, 4,000
feet above them.

The total mass of material transferred from within the mountain
to the surface by the explosive and effusive eruptions during the
four years since the beginning of volcanic activity at the summit of
Lassen Peak is very small as compared with the results of volcanic
eruptions generally, and yet its small size and high point of activity
may be important factors in discovering its cause.

In any discussion as to the cause of the recent eruptions a record
of the facts as to time and energy is fundamental.

The Forest Service at Red Bluff, W. J. Rushing in charge, fur-
nished most of the important data during the summer when the

12

VOLCANIC HISTORY OF LASSEN PEAK.

rangers were in the field, but at other times Miss Alice Dines, post-
master at Manton, and G. W. Olsen at Chester, both living in sight
of the mountain, supplemented the record. The eruptions have been
tabulated as to time, intensit}7, and duration, and the tabulation has

FIG. 7. — Lassen Peak in its twenty-ninth eruption, at 12.30 p. m. August 22, 1914.
as seen from Warner Valley near Lees, about 12 miles southeast of the crater.
The dust-ladened column of volcanic vapors rises more than 6,000 feet without
spreading.

a more or less evident bearing as to the efficiency of certain causes
that may affect the eruptions.

The variation as to time of day at which eruptions occur is very
irregular and one time of day appears about as favorable as another

VOLCANIC HISTORY OF LASSEN PEAK.

13

FIG. 9. — Eruption of October 6, 1915, seen from Manzanita Lake, at a distance of
5 miles. A column of " smoke," composed of steam, black with volcanic dust,
rose from the crater and at a height of about 3,000 feet above the crater spread
to the mushroom form shown in figure 9 about 30 minutes after the eruption began.
Photo © by C. Mullen, who took three views of the eruption, at 10-minute intervals,
to show its progress. The " lid " of new lava, formed about May 22, 1915, fills
the old crater at the time this view was taken, but can not be clearly seen on
account of new snow and cloud shadows.

14 VOLCANIC HISTORY OF LASSEN PEAK.

for eruption. Of the 220 eruptions up to the end of January, 1916,
143 occurred in the daytime, while 77 occurred at night; that is, be-
tween 7 p. m. and 7 a. m. In the daytime 57 eruptions occurred
between 7 and 11 a. m., 40 occurred about noon, between 11 a. m.
and 3 p. m., while between 3 and 7 p. m. 46 occurred. It has been
supposed that a greater supply of surface water might favor erup-
tion. If that is true, we should expect more frequent eruptions in
the late afternoon or early evening, when the day's supply of water
from melting snow is at its maximum. On the contrary, the morn-
ings have most eruptions, at a time when the daily heat and water
supply are near their minimum.

That the volcanic energy is not dependent upon the supply of sur-
face water to form steam is suggested by the fact that summer and
autumn, the dry season, with least water, have a greater number
(94) of eruptions than (84) the wet season of winter and spring.

In order to determine whether the volcano responds to the tidal
wave produced in the crust of the earth by the moon, Mr. Van
Orstrand has carefully considered 190 of the best recorded eruptions
and concludes that as yet the results are merely suggestive.

If we compare the number of corresponding seasonal eruptions in
1914 and 1915, the result appears significant. In the summer of
1914 there were 38 eruptions, but in 1915 only 17. In the autumn
of 1914 there were 56 eruptions, while in 1915 there were only 22.
Since the great eruption of May 22, 1915, when the new lava was
extruded and the Hat Creek country devastated, the number of erup-
tions has decreased and the decadence continues, but whether or not
the active period of Lassen Peak is approaching its close, although
probable, may be more certainly told hereafter.

With its comfortably active volcano, inviting cinder cones and
lava fields, vigorously boiling hot springs, mud lakes, and "mush
pots " for the volcanologist to study, and the glaciated divides and
canyons for the physiographer, in a setting of lovely scenery and
attractive camps, for the tourists all easily accessible, the Lassen
Peak region affords one of the most alluring and instructive spots
for a national park.

J. S. DILLER.

U. S. GEOLOGICAL SURVEY.